1. Technical Field
The present invention relates to a semiconductor device and a method of cutting an electrical fuse. More specifically, the present invention relates to a semiconductor device including an electrical fuse and a method of cutting an electrical fuse.
2. Related Art
A technology is conventionally known, in which a fuse is mounted in a semiconductor device, and the electric fuse is broken, so that a value of a resistor employed in the semiconductor device is suitably adjusted, or a failure element is separated and replaced into a normal element.
Typical manner for cutting a fuse includes cutting a fuse by irradiating a laser beam in a portion of the fuse and cutting a fuse by applying an electric current.
U.S. Pat. No. 4,064,493 discloses an electric fuse, which is capable of being broken by utilizing a phenomenon, in which a material constituting the electric fuse migrates by an electromigration.
Japanese Laid-open patent publication No. 2005-39,220 discloses an electric fuse, which is breakable with a smaller current. In Japanese Laid-open patent publication No. 2005-39,220, an electric conductor constituting an electric fuse is formed to have a geometry that the conductor is turned back for several folds. FIG. 7 is a plan view, showing an electric fuse disclosed in Japanese Laid-open patent publication No. 2005-39,220. In this case, a fuse 1100 includes two folds of turn-back.
The fuse 1100 includes a current inflow terminal 1101 and a current drain terminal 1102, and further includes a first forward path straight line 1103, a return path straight line 1104 and a second forward path straight line 1113 between both of the terminals. The fuse 1100 further includes a first perpendicular coupling portion 1106, which provides a coupling between the first forward path straight line 1103 and the return path straight line 1104, and a second perpendicular coupling portion 1107, which provides a coupling between the second forward path straight line 1113 and the return path straight line 1104. When a predetermined current is supplied from current inflow terminal 1101 into current drain terminal 1102 in the fuse 1100 having the above-described configuration, the heats generated in the hatched portions 1108 outside of the fuse 1100 are added to the heats generated in the hatched portions 1109 inside of the fuse 1100, accelerating the breaking of the return path straight line 1104 sandwiched with the hatched portions 1109. This provides easily cutting the fuse 1100.
Moreover, Japanese Laid-open patent publication No. 2005-57,186 has disclosed a configuration in which, when a current is applied to a fuse, heat generated in a portion of the fuse, which is to be cut, is trapped or accumulated in the neighborhood of the portion in the fuse, which is to be cut, by enclosing the portion with a plate.
Japanese Laid-Open Patent Publication No. 2004-214,580 discloses a fuse layout for improving yield and reliability by reducing the number of fuse cutting faults. FIG. 8 shows the fuse layout disclosed in the Japanese Laid-Open Patent Publication No. 2004-214,580. On a fuse layout 1010 formed by a interconnect electrode including a barrier metal layer made of a high melting point metal and a main-interconnect metal layer, a plurality of blow fuse portions 1011 and 1012 connected in series are formed. A fuse pad 1013 is formed on one end of the fuse portion 1011, a fuse pad 1014 is formed on a coupling portion coupling the fuse portion 1011 to the fuse portion 1012, and a fuse pad 1015 is formed on the other end of the fuse portion 1012. To flow a current across the fuse portion 1011, a voltage is applied between the fuse pads 1013 and 1014. To flow a current across the fuse portion 1012, a voltage is applied between the fuse pads 1014 and 1015. Based on suchlike a fuse layout 1010, when at least one of the plurality of fuse portions 1011 and 1012 is cut, the entire fuse layout is cut. It is thereby possible to greatly reduce a cutting fault ratio.
The present inventor has recognized as follows. The techniques disclosed in the U.S. Pat. No. 4,064,493 and the Japanese Laid-Open Patent Publication Nos. 2005-39,220 and 2005-57,186 have the following disadvantages. When the electrical fuse is insufficiently cut or constituent materials of the fuse migrates and the fuse is connected again after the fuse is cut once, it is impossible to accurately decide whether the fuse that should have been cut is cut. The probability of the reconnection or the like of the fuse is not so high, so that it is considered that the fuses provide satisfactory as long as they are used for ordinary operation. However, when requirement for the reliability of the semiconductor device is very strict or such a fuse is used in severe conditions, it is necessary to further improve retention characteristic for keeping cutting condition of the broken electrical fuse.
Moreover, according to the technique disclosed in the Japanese Laid-Open Patent Publication No. 2004-214,580, it is necessary to apply voltages to both ends of the respective fuse portions 1011 and 1012 so as to cut the fuse portions 1011 and 1012. As a result, these may cause a problem that the number of times of cutting processing increases and the configuration of the fuse is complicated.